One way of doing this can be very powerful for some people. You might like to try it. If you are praying and the Holy Spirit warns you that there is some bitterness or hatred in your heart, instead of trying to pretend that it is not there, admit its existence
Admit that you are bitter or hurt because of something someone did to you. Then, aware of the presence of Jesus, let the painful memory rise to the surface of your mind. Watch what happened at the time when you were hurt.
    Talk to Jesus about the hurts inside of yourself and ask him to touch and heal them just as the Good Samaritan poured oil on the wounds of the man left dying on the side of the Jerusalem to Jericho road. Tell him, too, about your feelings about the person or the people who have wounded you. Ask him to show you how he feels about those people. Ask  him to forgive you the grace to pray  the prayer he prayed from the cross when he was looking down on the people who were crucifying him: 'Father, forgive them.' When you can truthfully pray that prayer, imagine yourself whispering to the person: ' I really forgive you from my heart.'
    In may take several prayer times for you to reach the stage where you can pray such a prayer with honesty. When you can, you will feel very free.

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